High air velocity carburetor

ABSTRACT

A carburetor utilizing high air velocities, and having primary and secondary venturi circuits. The secondary circuit begins to function in response to the primary throttle position, with both circuits fully operating to supply fuel from the &#39;&#39;&#39;&#39;pickup point&#39;&#39;&#39;&#39; to wide open throttle. The primary circuit is designed to provide maximum manifold depressions of a high order at certain engine speeds.

United States Patent [72) Inventor Stephen Woods Harper Woods, Mich.(14155 Shadywood Drive, Apt. 63, Plymouth, Mich. 48170) [21) Appl. No.822,828 [22] Filed Apr. 9, 1969 [45] Patented Jan. 19, 1971Continuation-impart of application Ser. No. 629,488, Apr. 10, 1967, nowabandoned.

[54] HIGH AIR VELOCITY CARBURETOR 5 Claims, 3 Drawing Figs.

[52] U.S.Cl 123/127, 261/23, 261/39, 261/41, 261/43, 261/64 [51] Int. ClUFOZm 13/06 [50] Field ofSearch 261/43, 41.3,64,23, 50.1, 39.2DP;123/127 [56] References Cited UNITED STATES PATENTS 1,676,827 7/1928Howard et a1. 123/127 1,904,634 4/1933 Teeter.

Prentiss.

Farrell.

Olson Gretz.

Manning, Jr Bartholomew Martin.

Cook et a1. Kalert, .lr.

Smith Bickhaus et al.

Primary Examiner-Wendell E. Burns Atl0rneyWhittemore, I-Iulbert &Belknap PATENTEB JAN-1 9 I9" INVENTOR STEPHEN Woops av 4 iulilliuliil.

HIGH AIR VELOCITY CARBURETOR This application is a continuation-in-partof my copending application Ser. No. 629,488 filed Apr. 10, I967. SUMMA-RY OFTHEINVENTION I j The invention relates to a high'air velocitycarburetor and more particularly to a carburetor evidencingsubstantially increased performance characteristics.

I-Ieretofore. carburetors for high speed internal combustion enginescapable of about 2,800 rpm. or more at wide open throttle have requiredthe use of an accelerator pump and/or economizer to obtain full powerfrom the engine at above about 550 rpm. When the throttle was suddenlyopened full from a closed position at about 500 rpm. the depressionusually dropped to about .Sinches'of Mercury'or less, which ispractically O depression, with a resultant temporary loss of fuel flow.This has cre'atedehgine power loss problems which werecircumvented bythe use of an accelerator pump.

The present invention substantially eliminates the problems incident touse of an accelerator pump and provides improved engine accelerationperformance percent little fuel waste and hydrocarbon emission. Inaccordance with the inventive concept, a primary venturi system isutilized in intimate conjunction with a secondary venturi system wherebya substantially high air velocity is maintained in the carburetor at allloads and engine speeds, from idle "and off idle road load through midrange road load and wide open throttle. The primary ven turi systemsupplies about percent to 50 percent of the engines total airrequirements, while the secondary venturi system supplies about 50percent to90 percent of the requirements. i

The concept of the invention eliminates completely the need for theaccelerator pump andjeconomizer, and instead relies upon the secondaryventuri system which is added to a primary venturi system and whereinthe primary venturi is respectively which form vertically extendingprimary and secondary chambers 13 and 14 respectively. Chambers 13 and14 are separate, but converge below wall 15 into a common 7 throttlebore 16 formed in an annular throttle body 17 which has a entrancethroat l8. Bore 16 thus connects with and serves both the primary andsecondary systems, and is provided with a suitably actuated throttleplate I9 therein pivoted on pin 19'.

The wall of primary chamber 13 is provided intermediate its ends with-arestriction forming a main venturi 20 for the air flow. A boosterventuri 21 of greater restriction than main venturi 20 is disposed inthe throat ofthe latter. At the top or intake of chamber 13, a suitablechoke plate 22 is pivotally mounted on pin 22' and is actuated in anywell-known way.

Fuel from bowl 5 passes into chamber 13 and is mixed with air passingdownwardly therethrough. Assume that the engine is at curb idle and thatchoke plate 22 is at the substantially open position shown in full linesin FlG. 2, with throttle plate 19 also at substantially closed curb idleposition shown in full lines. Fuel from bowl 5 will be drawn up througha main jet member 23 in the lower portion of primary well chamber 9, andhence upwardly through a tubular idle channel 24 having an idle feedrestriction at its lower end. Channel 24 extends inwardly from chamber 9and across primary chamber 13 slightly upstream of venturis 20 and 21,as at 25, and hence downwardly through the carburetor wall and connectsto a restricted in sucha way as to provide substantially higher airvelocities than have been used heretofore. For the concept to operate,it has been found that the manifold depression must be substantiallyhigher than a mere few tenths of an inch of Mercury. i

The secondary throttle plate is fully responsive to the position of theprimary throttle plate, and in turn controls a secondary air valve. Therate ofopening of the latter valve may be controlled to produce thedesired acceleration rate, and various types of such valvesarecontemplated.

The accompanying drawing illustrates the best mode presentlycontemplated by the inventor for carrying out the invention. I

In the drawing:

FIG. 1 is a top plan view of a carburetor constructed in accordance withthe invention.

FIG. 2 is a section taken on line 2-2 of FIG. 1, with the fuel wellsrepositioned about 90 and the fuel bowl bisected and also repositionedfor purposes of clarity.

FIG. 3 is a sectional view of a second embodiment of secondary venturiair valve control means.

The carburetor illustratedin the drawings is of the single barrel type.However, any multibarrel construction may be used without departing fromthe spirit of the invention.

As shown in FIGS. I and 2 of the drawing, the carburetor is of the downdraft type and comprises a housing 1 which includes a fuel-receivingportion 2, a primary system portion 3 and a secondary system portion 4.

Fuel-receiving portion 2 comprises a chamber in housing 1 which forms afuel bowl 5 adapted to contain fuel which enters the chamber through asuitable fuel inlet 6 having a control valve 7 therein. Valve 7 isautomatically actuated by a float 8 which operates in the conventionalmanner to fuel fuel to flow into the bowl.

During operation of the carburetor, fuel from bowl 5 passes through apair of separate well chambers 9 and 10 and into primary and secondaryportions 3 and 4 respectively, as will be described.

Primary and secondary portions 3 and 4 comprise a pair of closelyadjacent generally cylindrical members 11 and I2 passageway 26 inthrottle body 17.,Passageway 26 is provided with a lower curb idle port27 andan upper idle transfer port 28 for passage of fuel at idle intothe engine intake manifold. Ports 27 and 28 straddle throttle plate 19when the latter is in its curb idle position.

In the curb idle position, fuel will flow through curb idle port 27,which is adjustable as to size by an idle adjustment screw 29 to provide.the proper idle fuel mixture. As throttle plate 19 opens, upper idletransfer port 28 is also exposed, adding additional fuel as the enginerequires it. Further opening of throttle plate 19 gradually reduces themanifold depression, but also increases the air flow velocity pastportion 25 of channel 24. A small downwardly extending idle bleedopening 30 is disposed in portion 25, and as the air velocity increasespast the opening, an increasing depression is created at the opening.Finally, when throttle plate, 19 has reached a certain open position,the depression at idle bleed opening 30 will reach equilibrium with themanifold depression. Fuel will then no longer flow through idle channel24 to ports 27 and 28, but will instead fall through opening 30 pastventuris 21 and 20 and through throttle bore 16 into the enginemanifold. At the same time, fuel in bowl 5 will pass upwardly through acylindrical well housing 31 which surrounds channel 24 in the well andhence discharges from a tube 3.2 in the area of booster venturi 21 andis drawn downwardly through throttle bore 16.

It is at this pickup point" that the secondary venturi system takesover.

Throttle plate 19, which is common to both venturi systems at thethrottle bore 16, is connected, as by pivotal links 33, 34 and 35 to asecondary throttle plate 36 pivotally'mountedon pin 36' which isdisposed in secondary chamber 14 adjacent the lower end of wall 15. Inaddition, an air valve which may take the form of a pivotal plate 37mounted on pivot pin 37', is

disposed at the top or air intake of chamber 14. Fuel from fuel bowl 5is supplied to secondary chamber 14 through a system of supply passageswhich are substantiallysimilar to those in the primary venturi system,and which supply fuel to the secondary venturi 38. The idle channel 24and associated ports are not duplicated in the secondary system.

During initial opening of throttle plate 19, secondary throttle plate 36remains substantially closed due to the lost motion built into thelinkage system by reason of the fact that the upper end of link 34 has aslidable connection with slot 39 in link 35. At the so-called pickuppoint," plate 19 is in the predetermined dotted position shown as A inFIG. 2. As throttle plate 19 is opened further, the linkage causesthrottle plate 19 is opened further, the linkage causes throttle plate36 to begin to open. By varying the linkage construction. the rate ofopening of plate 36 relative to plate 19 can be changed to providedifferent fuel-air mixtures at different loads and engine speeds to suitperformance requirements.

As secondary throttle plate 36 opens, air valve plate 37 is subjected toincreased downward air pressure tending to open it from its generallyclosed position shown in full lines in FIG. 2. As this occurs,additional air flow is generated through secondary chamber 14 andthrough bore 16. Depending upon the particular engine requirements, theresponsiveness of plate 37 to air pressure, and thus the plate openingrate, can be controlled.

In addition, it is preferable to prevent sudden snaplike opening of thevalve 37. For this purpose, control means are provided to govern ordampen the opening rate of the valve.

One embodiment of control means is shown in FIGS. 1 and 2, wherein aplurality of pressure relief openings 40 are formed in plate 37, whichallow air to filtrate through the valve at a predetermined calibratedrate. This reduces the initial force exerted on plate 37 when secondarythrottle plate 36 is opened, and also provides a controlled initial rateof opening. Openings 40 are properly calibrated and disposed in thepositions shown on an arc at progressively increasing distances from thepivot pin 37 for plate 37.

A second embodiment is shown in FIG. 3, wherein valve plate 37 issecured through suitable pivotally connected links 41, 42 to pneumaticdashpot which includes a plunger 43 movable within a cylinder 44.Plunger 43 is preloaded, as by a compression spring 45 which can bechanged to provide the desired rate of dashpot operation. A bleedopening 46 in the wall of cylinder 44 controls the flow of air out ofthe dashpot chamber and may connect to primary chamber 13, whereinincreased air flow through the chamber puts a vacuum on plunger 43 toassist in overcoming the force of spring 45.

The embodiments of openings 40 shown in FIGS. 1 and 2 and the dashpotshown in FIG. 3 provide controlled initial restraint to the movement ofvalve plate 37. Other resistance means may be provided without departingfrom the spirit of the invention. I

It has been found that the combined primary and secondary systems willonly function in a manner which eliminates the requirement for anaccelerator pump and economizer if very high air flow velocities areutilized. These velocities must be reflected in the following manifolddepressions for the concept of the invention to operate:

1. To eliminate accelerator pump:

At Wide Secondary Throttle Plate lnoperative:

A. Manifold depression must be not less than 3 inches of Mercury 3,6001,200 engine r.p.m.

B. Manifold depression must be not less than 7 inches of Mercury 0 3,600engine r.p.m.

II. To eliminate economizer:

At pickup point" with Secondary Throttle Plate 36 Beginning to Open:

A. Manifold depression must be not less than inches of Mercury 0 700engine r.p.m.

B. Manifold depression must be not less than 9 inches of Mercury 0 3,000engine r.p.m.

It will be understood that there may be small reductions at times inthese stated minimum depressions. within the scope of the invention.While I have determined that reduction of depression below the statedminimums by as much as .25 inches Hg, at wide open primary throttle maybe unacceptable, reductions of depression below the stated minimums byas much as .5 inches Hg. at the "pickup point" may still producesatisfactory results.

If the depression values are permitted to fall below those given above,it is been found that major problems of engine hesitation, stumbling andstalling develop. This has been found to be true, regardless of thedisplacement of the particular engine.

In accordance with the invention, the area of main venturi will have tobe restricted to a given maximum, which in turn will depend on thedisplacement of the particular engine or engines with which thecarburetor is to be used. If the venturi area is smaller than thedetermined maximum. no harm will result. since this will increase thedepression above the minimum values given above. and the smoothperformance of the carburetor will be maintained.

An example of determining the theoretical main venturi size to satisfythe requirements for an engine of given displacement is as follows:

It will be assumed that the engine is four-cycle with 290 cubic inches.It is first necessary to calculate the engine air requirements. It canbe shown that:

(A) (1) 100.6 c.f.m. at 1,200 r.p.m. (A) (2)==1.666 c.f.s. at 1,200r.p.m. (B)(1)=302.0 c.f.m. at 3,600 r.p.m. (B) (2)=5.033 c.f.s. at 3,600r.p.m.

displacement X air flow, cu. ft./min.=

A. 3 inches Hg. .25 ft. Hg.

B. 7 inches Hg. .5833 ft. Hg.

It is now necessary to convert feet of Mercury to feet of air. Using theformula:

B. -y,, specific weight of Hg. 845.3 lb./cu.ft.

C. h ft. of flowing air 7 Specific weight of air .073 lb./cu.ft. it ispossible to show the following:

A. At 3 in. or .25 ft. of Hg., flowing air= 2894.7 cu. ft.

B. At 7 in. or .5833 ft. of Hg, flowing air 6754.3 cu. ft.

The law of continuity of flow is: Q AV, where 1. Q Quantity offluid airflowing in c.f.s.

2. A Cross-sectional area of the restriction at point of velocitypressure in sq. ft.

3. V Fluid air velocity in f.p.s.

=v v where:

(A) g= Gravitational acceleration in ft./sec./sec. (B) h =Vel0city headin feet of fluid flowing air= h (from above) Since h =h and Q=AV,

and

it is possible to show that A. A .84 in. diameter venturi at 1,200r.p.m.

B. A 1.047 in. diameter venturi at 3,600 r.p.m.

Thus, a venturi of .84 in. diameter would satisfy the above specifiedrequirements as to minimum manifold depression. It would be suitable forboth 1,200 r.p.m. and 3,600 r.p.m. since it would give a value above theminimum at 3,600 r.p.m. The venturi of 1.047 in. diameter would notsatisfy the requirements, since it would give a value below the minimumat 1,200 r.p.m.

The above example is based on a theoretical engine of 100 percentefficiency, rather than the normal 80 percent -85 percent of most highcompression engines. in addition, frictional losses in the airflow, aswell as temperature and barometric variations have not been considered.

Perhaps the biggest source of friction in a carburetor is in the venturirestriction itself and in the size of the throttle bore 16 and airchamber 13. It can be shown that, with a given manifold depression, asthe difference between venturi area and throttle bore area increases,the airflow capacity of the carburetor increases. Thus, to remain abovethe minimum manifold depression values given above, the size of venturi20 should be determined, and the throttle bore adjusted in size to givethe desired airflow characteristics. in addition to, or in place ofthrottle bore size variations. the airflow characteristics may also bechanged by changing the distance between throttle bore 16 and venturi20. Also, the size and positioning of booster venturi 21 and othercomponents within chamber 13 will have some bearing on the air flow.But, the proper interrelationship of size and position between throttlebore 16 and venturi 20 will produce most if not all desired airvelocities. Properair box studies will provide the information necessaryto obtain these interrelationships.

The size of main venturi 20 needed to maintain the desired high manifolddepression is substantially smaller than in conventional carburetorsystems. However, there is no power loss when going into midrange andhigh range carburetor operation because of secondary venturi portion 4,which provides increased air flow and fuel availability automatically inresponse to the position of throttle plate 19. At the pickup point"described above, portion 3 is functional and portion 4 begins tooperate. And both portions operate at wide open throttle. There is thussufficient depression to provide fuel to the primary portion 3 at allranges of carburetor operation, as well as to the secondary portion 4above the pickup point."

The concept of the invention provides high air velocity through thecarburetor at all engine speeds and load with little if any loss ofengine power output. Fuel evaporation within the carburetor is at amaximum. with fuel dumping being substantially eliminated. A carburetorembodying the inventive concept has fewer parts than heretofore withoutsacrificing fuel delivery characteristics. In addition. a carburetordesigned in accordance with the invention can be effectively used on avariety of high speed engines with differentdisplacements, regardless ofthe type of fuel used.

While the embodiment described and shown utilizes only a single primaryand single secondary system, any suitable multiples of primary and/orsecondary may be used without departing from the spirit of theinvention.

1 claim: 1. In a carburetor for a high speed compression engine having aknown displacement, a main discharge throttle bore, separate primary andsecondary air passages leading to said throttle bore, a main throttlevalve in said throttle bore, a normally closed secondary throttle valve:in said secondary air passage, means responsive to movement of saidthrottle valve past a predetermined partially open position to open saidsecondary throttle valve, means for maintaining said seconda ry throttlevalve, means for maintaining relatively high velocity air flow throughthe carburetor at all engine speeds and for providing the followingmanifold depressions during engine operation:

1. depression not less than 3 in. Hg. at 1.200 engine r.p.mv 2.depression not less than 7 in. Hg. at 3,600 engine r.p.m. said secondmentioned means comprising air restrictive venturi means ofpredetermined] cross section in ac cordance with said known enginedisplacement disposed in said primary air passage, an air valve in saidsecondary air passage upstream from said secondary throttle valve forcontrolling the flow of air into said secondary air passage upon openingof said secondary throttle valve. damper means for retarding the initialrate of opening of said air valve, and fuel inlets in said primary airpassage and in said secondary air passage between said secondarythrottle valve and said air valve. 2. The structure defined in claim 1,wherein said damper means includes aperture means formed in said airvalve.

3. The structure defined in claim 1, wherein said damper means comprisesa spring-biased pneumatic dashpot connected to said air valve, thespring-biasing force of said dashpot resisting opening of said airvalve, and air discharge means connecting said dashpot with said primaryair passage so that increasing air flow through said primary air passageplaces a vacuum on said dashpot tending to overcome the spring-biasingforce.

4. The structure defined in claim ll, wherein said second mentionedmeans provides the following manifold depressions during engineoperation: 7 l

l. depressionsnot less than 5 in. Hg. at 700 engine r.p.m.

2. depressions not less than 9 in. Hg. at 3,000 engine r.p.m.

5. The structure defined in claim ll, wherein said second mentionedmeans provides the following manifold depressions during engineoperation:

1 With said second air passage closed to air flow:

a. depression not less than 3 in. Hg. at 1,200 engine r.p.m. b.depression not less than 7 in. Hg. at 3,600 engine r.p.m. 2. with saidthrottle valve moving just beyond said partially open position: a.depression not less than 5 in. Hg. at 700 engine r.p.m. b. depressionnot less than 9 in Hg. in. Hg at 3,000 engine r.p.m.

1. In a carburetor for a high speed compression engine having a knowndisplacement, a main discharge throttle bore, separate primary andsecondary air passages leading to said throttle bore, a main throttlevalve in said throttle bore, a normally closed secondary throttle valvein said secondary air passage, means responsive to movement of saidthrottle valve past a predetermined partially open position to open saidsecondary throttle valve, means for maintaining said secondary throttlevalve, means for maintaining relatively high velocity air flow throughthe carburetor at all engine speeds and for providing the followingmanifold depressions during engine operation:
 1. depression not lessthan 3 in. Hg. at 1,200 engine r.p.m.
 2. depression not less than 7 in.Hg. at 3,600 engine r.p.m. said second mentioned means comprising airrestrictive venturi means of predetermined cross section in accordancewith said known engine displacement disposed in said primary airpassage, an air valve in said secondary air passage upstream from saidsecondary throttle valve for controlling the flow of air into saidsecondary air passage upon opening of said secondary throttle valve,damper means for retarding the initial rate of opening of said airvalve, and fuel inlets in said primary air passage and in said secondaryair passage between said secondary throttle valve and said air valve. 2.with said throttle valve moving just beyond said partially openposition: a. depression not less than 5 in. Hg. at 700 engine r.p.m. b.depression not less than 9 in Hg. in. Hg at 3,000 engine r.p.m. 2.depressions not less than 9 in. Hg. at 3,000 engine r.p.m.
 2. Thestructure defined in claim 1, wherein said damper means includesaperture means formed in said air valve.
 2. depression not less than 7in. Hg. at 3,600 engine r.p.m. said second mentioned means comprisingair restrictive venturi means of predetermined cross section inaccordance with said known engine displacement disposed in said primaryair passage, an air valve in said secondary air passage upstream fromsaid secondary throttle valve for controlling the flow of air into saidsecondary air passage upon opening of said secondary throttle valve,damper means for retarding the initial rate of opening of said airvalve, and fuel inlets in said primary air passage and in said secondaryair passage between said secondary throttle valve and said air valve. 3.The structure defined in claim 1, wherein said damper means comprises aspring-biased pneumatic dashpot connected to said air valve, thespring-biasing force of said dashpot resisting opening of said airvalve, and air discharge means connecting said dashpot with said primaryair passage so that increasing air flow through said primary air passageplaces a vacuum on said dashpot tending to overcome the spring-biasingforce.
 4. The structure defined in claim 1, wherein said secondmentioned means provides the following manifold depressions duringengine operation:
 5. The structure defined in claim 1, wherein saidsecond mentioned means provides the following manifold depressionsduring engine operation: